The present invention relates to a sampling vessel for thermal analysis of molten metal, and more particularly to a sampling vessel for, when a cast material of cast iron, aluminum, an alloy thereof, or the like is to be produced, thermally analyzing the structure of the cast material in front of a furnace.
When cast iron, a light metal such as aluminum, an alloy thereof, or the like is to be cast, the following method is generally adopted for examining the structure of the melt in front of a furnace. The melt is poured into a sampling vessel for thermal analysis provided with a temperature sensor, and a cooling curve of the melt is obtained from an output of the temperature sensor.
As a sampling vessel of this kind, a so-called cup-type vessel is often used. Such a cup-type vessel includes: a vessel body which is made of a heat resisting material, which has a substantially cylindrical bottomed shape, and which comprises a sample chamber having an opening in an upper end; and a temperature sensor such as a thermocouple which is passed through the bottom wall of the sample chamber to be located in the sample chamber. By using a ladle or a dipper, the melt is poured into the sampling vessel from the furnace in which the metal is molten.
As exemplarily shown in a longitudinal section view of FIG. 10, such a conventional cup-type sampling vessel usually has a sample chamber 101 measuring about 30 mm in diameter and about 50 mm in depth. A temperature sensor 102 is placed in a middle portion in depth of the sample chamber 101, that is, in a position which is separated by about 25 mm from an opening 101a in the upper end of the sample chamber 101.
Another kind of known sampling vessel is a so-called probe-type sampling vessel which is disclosed in Japanese Patent Publication (Kokai) No. 2000-131311. The probe-type sampling vessel comprises: an runner which is adjacent to a sample chamber having an opening in the upper end, the lower end of which is opened, and which communicates with the opening of the sample chamber; an exhaust passage which communicates with the opening of the sample chamber, and the upper end of which is opened in a higher position than the opening of the sample chamber; and a sensor holder which is formed above the sample chamber, and which holds a temperature sensor that is inserted from the opening of the sample chamber into the sample chamber. The sampling vessel has a structure in which these components are integrally formed by a heat resisting material. In the conventional probe-type sampling vessel, the shape and dimensions of the sample chamber are the same as those of the above-described cup-type vessel.
The sampling vessel is produced in the following manner. Two or right and left members respectively having shapes which are formed by dividing the vessel by a dividing plane along the center axis of the sampling vessel, that is, by a dividing plane in the longitudinal direction of the vessel are produced. The members are bonded together in the dividing plane with an adhesive agent.
The probe-type sampling vessel is immersed in the melt, so that the melt is caused to flow into the sample chamber through the runner in which the lower end is opened. In accordance with the flow-in, the air in the interior of the vessel including the sample chamber is exhausted to the outside through the exhaust passage in which the upper end is opened. Accordingly, in the probe-type sampling vessel, the sample chamber can be filled with the melt without using a ladle or a dipper.
In both the above-mentioned conventional cup-type and probe-type sampling vessels, the time required for analysis is relatively long, and the temperature fall rate in eutectic, i.e., the gradient of a cooling curve in eutectic is relatively large. Thus, the vessels involve a problem in that the analytic procedure for determining the eutectic point is complicated.
In the conventional probe-type sampling vessel, the structure is complicated, and the bonding area for the two members is large, thereby producing a problem in that the workability of assembly is poor. Since the two members have a slim shape in which the longitudinal size is larger than the lateral size, each member easily warps during a process of firing the member. Such warping causes a failure to be produced in bonding the two members together. Since the bonding plane exists in a position where the sample chamber is divided into two portions, the adhesive agent may enter in the sample chamber. In this case, the adhesive agent may serve as an impurity to contaminate the melt. For these reasons, it is necessary to provide a large number of inspection steps.
In the conventional probe-type sampling vessel, the exhaust passage is bent in the vessel. When the flow-in melt is cooled, therefore, the metal may obstruct the exhaust passage in the inside thereof, and the gas may not be exhausted. In this case, the sampled melt may be caused by the gas pressure to flow backward or to be diverted, thereby producing the possibility that a predetermined amount of melt cannot be sampled.
Moreover, the conventional probe-type sampling vessel involves an additional problem in that, because of the complication of the inner passage and the large outer dimensions of the whole vessel, a large pushing force is required for immersing the vessel into the melt.
The invention has been conducted in view of the above-mentioned circumstances. It is a primary object of the invention is to provide a sampling vessel for thermal analysis of molten metal in which the time required for analysis a can be shortened and the temperature change rate in eutectic can be reduced as compared with the conventional cup-type and probe-type sampling vessels, so that the eutectic temperature can be obtained easily accurately for a short time.
It is another object of the invention is to provide a probe-type sampling vessel for thermal analysis of molten metal in which the structure is simple, and the production and inspection steps can be remarkably simplified as compared with the conventional probe-type sampling vessel, and the pushing force required for immersing the vessel into the melt can be reduced.
It is a further object of the invention is to provide a sampling vessel for thermal analysis of molten metal in which there is no possibility that the melt is solidified in the exhaust passage and the air is blocked from being exhausted, as compared with the conventional probe-type sampling vessel.
In order to attain the primary object, the sampling vessel for thermal analysis of molten metal according to the invention is a sampling vessel for thermal analysis of molten metal which is made of a heat resisting material, which has a substantially cylindrical bottomed shape comprising a sample chamber having an opening in an upper end, and in which a temperature sensor is passed through a bottom wall of the sample chamber to be located in the sample chamber, and is characterized in that the sample chamber has a diameter in a range of 16 to 24 mm, and a depth of 36 mm or more, and the temperature sensor is located at a depth in a range of 7 to 22 mm away from the upper-end opening of the sample chamber.
In order to also attain the primary object, the sampling vessel for thermal analysis of molten metal according to the invention is a sampling vessel for thermal analysis of molten metal including: a cylindrical bottomed sample chamber which has an opening in an upper end; a runner which is formed in adjacent to the sample chamber, in which a lower end is opened, and which communicates with the opening of the sample chamber; an exhaust passage which communicates with the opening of the sample chamber, and in which an upper end is opened in a higher position than the opening of the sample chamber; and a sensor holder which is formed above the sample chamber, and which holds a temperature sensor that is inserted into the sample chamber through the opening of the sample chamber, the sample chamber, the runner, the exhaust passage, and the sensor holder being integrally formed by a heat resisting material, and is characterized in that the sample chamber has a diameter in a range of 16 to 24 mm, and a depth of 36 mm or more, and the temperature sensor is located in a position in a range of 7 to 22 mm away from a bottom wall of the sample chamber.
In order to attain the other object, the sampling vessel for thermal analysis of molten metal according to the invention is characterized in that the sampling vessel for thermal analysis of molten metal is configured by two or upper and lower members respectively having shapes which are formed by dividing the vessel by a dividing plane that perpendicularly crosses a center axis of the vessel in a position which is above the sample chamber and not in the sample chamber, and the members are bonded together in the dividing plane.
In order to attain the further object, the sampling vessel for thermal analysis of molten metal is characterized in that the runner and the exhaust passage communicate with each other on a straight line.
In the invention of each of the above-mentioned claims, preferably, a circumference wall of the sample chamber has a thickness of 5.5 mm or more.
The invention has been conducted by eagerly studying the shapes and dimensions of portions of a sampling vessel for thermal analysis of molten metal, so as to optimize them. According to experiments, the diameter of the sample chamber is preferably set to be in the range of 16 to 24 mm, and more preferably in the range of 18 to 21 mm. When the diameter of the sample chamber is smaller than 16 mm, the temperature fall rate in eutectic is large, so that it is difficult to determine the eutectic temperature. When the diameter exceeds 24 mm, the time required for analysis is disadvantageously prolonged, and hence such a large diameter is not preferable.
The depth of the sample chamber is preferably set to be 36 mm or more, and more preferably 40 mm or more. When the depth is less than 36 mm, the temperature fall rate in eutectic is large, so that it is difficult to determine the eutectic temperature.
Moreover, the distance from the upper-end opening of the sample chamber to the temperature sensor in a cup-type sampling vessel, and that from the bottom wall of the sample chamber to the temperature sensor in a probe-type sampling vessel are preferably set to be in the range of 7 to 22 mm, and more preferably in the range of 9 to 17 mm. When the distance from the upper-end opening of the sample chamber to the temperature sensor in the cup-type sampling vessel, or the distance from the bottom wall of the sample chamber to the temperature sensor of the probe-type sampling vessel is less than 7 mm, the melt in the position where the temperature sensor is disposed is easily cooled, so that it is impossible to obtain a good cooling curve. When the distance exceeds 22 mm, the temperature fall rate in eutectic is large, so that it is difficult to determine the eutectic temperature.
With respect to other dimensions of the sample chamber, the thickness of the circumference wall is preferably set to be 5.5 mm or more, and more preferably 6 mm or more. When the thickness is less than 5.5 mm, the temperature fall rate is large, and the time required for analysis is prolonged.
The above-mentioned shapes and dimensions of the various portions of the sample chamber are common to the cup-type sampling vessel and the probe-type sampling vessel. When the configurations of the inventions are adopted, the eutectic temperature can be easily accurately known for a short analysis time.
The sample chamber having the above-mentioned shape and dimensions has smaller outer dimensions as compared with a conventional sample chamber. When the sample chamber is applied to a probe-type sampling vessel, therefore, the dimensions as a whole can be miniaturized as compared with the conventional one, and it is possible to attain reduction of the pushing force which is required for immersing the vessel into the melt.
With respect to the probe-type sampling vessel, when a configuration is employed in which the sampling vessel consisting of the sample chamber, the runner, the exhaust passage, and the sensor holder is configured by two or upper and lower members respectively having shapes which are formed by dividing the vessel by a dividing plane that perpendicularly crosses the center axis of the vessel in a position which is above the sample chamber and not in the sample chamber, and the members are bonded together in the dividing plane, the sampling vessel can attain the following advantages as compared with a conventional probe-type sampling vessel which is divided by a dividing plane along the center axis of the conventional vessel, i.e., divided into a right and a left members. Since the bonding area is reduced, the bonding operation can be simplified. The occurrence of warping in a process of firing each member can be avoided because of the reduced aspect ratio of each member. Since the bonding plane does not cross the sample chamber, the possibility that the adhesive agent may enter the sample chamber can be eliminated. Therefore, the production and inspection steps can be simplified.
Moreover, when a configuration is employed in which the runner and the exhaust passage communicate with each other on a straight line, the internal structure of the probe-type sampling vessel is simplified, and the melt can smoothly flow. Thus, it is possible to suppress the cooling of the melt in the runner. The smooth flow of the melt due to the simplified internal structure of the probe-type sampling vessel contributes together with the above-mentioned reduced outer dimensions to reduction of the pushing force in the process of immersing the vessel into the melt.